Could you probably post your question into the udk forum 
https://forums.epicgames/forums/366-UDK This forum is just for UE4 stuff
2nd problem:
When the spaceship is also dark, you will have to create a 2nd uv channel + lightmap
Could you probably post your question into the udk forum https://forums.epicgames/forums/366-UDK This forum is just for UE4 stuff
2nd problem:
When the spaceship is also dark, you will have to create a 2nd uv channel + lightmap